On 12/05/2013 07:44 AM, Leonardo Marsaglia wrote: > Well I tried like Andy said increasing the ferror and I can work a lot > better. Also my acceleration was too much so I decreased it and now I have > a error of 0.2 mm without fine tunning and with the motor moving air for > now, I guess that when it's attached to the screw this will be a lot > better. > > One thing about that error is that the motor keeps oscillating between > those two points but never stops. Is this a normal behaviour on a bad > tunned motor? If I tune it well I would expect the oscillation to dissapear > or at least stop at some moment? > > Thanks as always! > > Leonardo.
There often is a difference between the feedback resolution and the motor resolution. For instance, if your motor can be moved to within a degree of position, but your encoder feed back can report in tenths of a degree. When you command a position, the motor will get to within a degree, but your encoder says you are not there yet. Over time, your PID will increase its power to make a correction and finally move the motor. The motor moves another degree and over shoots the original position, the encoder reports this and the PID tries to correct in the other direction, causing an oscillation of +/- one degree or more. There should be a deadband parameter you can set to tell the PID to ignore a certain amount of error. Using HALscope to show the position or velocity command and feedback show show this hunting and may give you an idea how much there is. Posting your HALscope screen may help too. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/ ------------------------------------------------------------------------------ Sponsored by Intel(R) XDK Develop, test and display web and hybrid apps with a single code base. Download it for free now! http://pubads.g.doubleclick.net/gampad/clk?id=111408631&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
